In general, volumetric fluid compressors of this kind comprises a suction chamber 100 and a discharge chamber 102 on the rear side of a housing 1, as shown in FIG. 13, with an offset shaft 8 being connected to the inner end of a rotary shaft 6 which in turn is passed through the front end side of the housing. A movable scroll member 9 is rotatably mounted to the offset shaft 8 by a radial bearing 10 and, for preventing the rotation of the movable scroll member 9 about its own axis, a stationary ring 11 is fitted to the inner periphery of the housing 1. Refrigerant gases are directed from a working chamber 101 defined at the rear side of the stationary ring 11, towards a radial bearing 21 for the rotary shaft 6, a shaft sealing device 7 and a thrust bearing 22 for a balance weight 14, for cooling and lubrication of these components by way of a channel 11c in the ring 11 and a channel 1b in the housing 1. Refrigerant gases are also supplied centrifugally to the radial bearing 10 for cooling and lubrication thereof from a passage 23 extending obliquely on the rotary shaft 6 and the offset shaft 8.
With such conventional lubrication system, a sufficient centrifugal force may not be realized because of reduced offset amount of the offset shaft 8. Such inconvenience may be more outstanding during low speed revolution to thereby decrease in lubrication and cooling effects. Moreover, the rotary shaft 6, balance weight 14 and the bearings 10, 21 are mounted in their entirety in a space defined by the stationary ring 11 on the front side of the housing 1, thus proving to be a hindrance to intrusion of the fresh refrigerant gases and decreasing the cooling and lubrication efficiency.